The invention relates generally to concentrating optics, and more particularly to light concentrating modules and methods for generating power.
Light concentrating modules (e.g., solar concentrating collectors) exist today for generating electricity with a photovoltaic (PV) cell. Separate light concentrating modules exist today for capturing thermal energy through the transfer of heat into a working fluid. In both types of modules, a substantial portion of the available energy from the sun is not captured and converted into usable energy. For example, in the case of collectors that generate only electricity, a substantial amount of thermal energy is dissipated into the surroundings. By capturing and applying this waste heat, it would be possible to increase the overall energy conversion efficiency of the module, increase the energy production per square meter of the installed module, and enable applications such as hot water heating, space heating, and air conditioning in addition to electricity generation.
At least one conventional system has been proposed to combine electricity and heat generation. In this combined system, a trough-type reflector configuration is used where light rays are reflected by a trough-shaped optical element to concentrate the light into a linear focal region. The trough-type configuration, however, provides relatively low light concentration levels (e.g., below 100× and more typically somewhere in the range of 10× to 40×). Also, the trough-shape optical element is difficult to adjust for tracking the light source which may negatively affect the conversion efficiency. Systems of this type generally rely on silicon-based PV cells which are less efficient than available alternatives such as III-V based multijunction solar cells. Therefore, while attempting to make use of more of the available energy from the sun, the conventional system relies on sub-optimal solar collector configurations with low concentration levels and low energy conversion efficiencies.
Other known light concentrating systems use optical elements (e.g., dishes) that provide a point focal region. Conventional systems that use a point focal region are typically designed only for electricity generation and are unable to capture the dissipating thermal energy. Those that may be targeted for capturing the thermal energy in addition to electric energy suffer from inefficient capture of the light rays caused by shading of the primary reflective surface by either secondary optical elements or the receiver system itself, thereby reducing the quantity of light arriving at the primary reflector and subsequently the receiver. Another cause of inefficient capture of the light rays is the use of too many optical elements, which may introduce significant loss of light rays due to absorption and/or reflection losses at each optical interface.
Furthermore, in order to generate sufficient quantities of power, conventional point focal light concentrators may be assembled into an array. This necessitates the fabrication, assembly, inter-connection, and installation of a large number of such light concentrators which can cause the cost of a complete power generating system based on light concentrators to be quite high. In addition, the arrays may suffer from reduced power production per unit area due to incomplete utilization of available space. For example, gaps may exist between light concentrating modules when arranged in an array.
Another problem with current light concentrating systems is that they are not designed for easy maintenance, repair, or component upgrades over the envisioned lifetime of the system. Many are constructed from materials or configured in such a way that they are not designed to survive the rigors of many years of consistent operation in the intended environment without significant performance degradation. In addition, many of these systems are not designed for high-volume manufacture at low cost, while maintaining long term reliability. All of these factors combine to make the initial installation cost, as well as the total cost of ownership, several times higher than the cost of competing, non-solar sources of energy.
Thus, there is a need for co-generating light concentrating modules and methods that operate with sufficient PV conversion efficiencies, while also providing thermal energy. There is also a need for light concentrating modules that maximize power production for the given area, maximize capture and energy conversion of light rays, and accomplish this in a manner that reduces costs related to light concentrator fabrication, assembly, inter-connection, and installation. In addition, there is a need for a light concentrating module that may be easily repaired, maintained, or updated throughout the lifetime of a system.